PITTSBURGH -- The Pittsburgh Steelers have placed cornerback Curtis Brown on injured reserve, ending the fourth-year veteran's season and possibly his career in Pittsburgh.

Brown tore the ACL in his left knee this past Sunday while covering a punt. The Steelers have promoted cornerback Isaiah Green from the practice squad to take Brown's spot on the 53-man roster and signed cornerback Devin Smith to the practice squad.

Brown will be an unrestricted free agent at the start of the league's new year in March, and he has ended up on injured reserve in all three of his NFL seasons.

More significant to his future with the Steelers: Brown has played primarily on special teams and not developed into the kind of cornerback who can start or even help on defense.

If the Steelers bring back Brown for his special-teams play it will be at a minimal cost, even though they need to develop some young cornerbacks.

The Steelers have used a pair of third-round draft picks on cornerbacks since 2009 and neither is on the 53-man roster.

Keenan Lewis signed with the Saints last March, parlaying a couple of solid seasons for the Steelers into a big contract with his hometown team.